Incremental Geometry Approximation With Procedural Support

/* definitions: the current root node can be either a root specified by a render call, or an instance of procedural object. */

/* to update the accel tree for current root node (the accel tree must be dirt & rebuilt for each frame) : */

/* 1. travese accel tree (from current root node) to collect all cached tessellations into a local cache */

/* 2. travese DAG (from current root node) to build tessellations with this local cache */

/* 3. delete all unreferenced tessellations in the local cache */